WO2013018036A1

WO2013018036A1 - Reverse osmosis desalinator

Info

Publication number: WO2013018036A1
Application number: PCT/IB2012/053915
Authority: WO
Inventors: Alberto VINCIGUERRA; Angelo Reboa; Lorenzo BRUZZONE; Marco TOSATO; Luca Valenti
Original assignee: Rex Srl
Priority date: 2011-08-02
Filing date: 2012-07-31
Publication date: 2013-02-07
Also published as: ITGE20110083A1

Abstract

Reverse osmosis desalinator comprising an inlet conduit for a high salt concentration liquid to be treated, a feed pump for supplying said liquid to be treated into one or more filter units comprising at least one osmotic membrane, which one or more filter units are connected to at least one outlet conduit for the permeate liquid, i.e. a liquid whose salt content is lower than that of the liquid to be treated, and to at least one outlet conduit for the concentrate liquid, i.e. the liquid part having a high salt content, with the salt fraction extracted from the permeate liquid dissolved therein, and which concentrate liquid is to be discarded, further comprising at least one energy recovery device for recovering the kinetic and/or pressure energy of said concentrate liquid at the outlet of said one or more filter units, wherein said energy recovery device further consists of at least one hydraulic turbine at the outlet of said one or more filter units, which hydraulic turbine is mechanically connected to drive an auxiliary pump at the inlet of said one or more filter units and connected in series with said feed pump.

Description

REVERSE OSMOSIS DESALINATOR

The present invention relates to a reverse osmosis desalinator comprising an inlet conduit for a high salt concentration liquid to be treated, a feed pump for supplying said liquid to be treated into one or more filter units comprising at least one osmotic membrane, which one or more filter units are connected to at least one outlet conduit for the permeate liquid, i.e. a liquid whose salt content is lower than that of the liquid to be treated, and to at least one outlet conduit for the concentrate liquid, i.e. the liquid part having a high salt content, with the salt fraction extracted from the permeate liquid dissolved therein, and which concentrate liquid is to be discarded, further comprising at least one energy recovery device for recovering the kinetic and/or pressure energy of said concentrate liquid at the outlet of said one or more filter units.

A reverse osmosis desalinator is a known device, which is widely used to remove the salt fraction from a sal -containing liquid, generally water and particularly seawater, to obtain a permeate liquid having a low salt content.

In the case of seawater, the desalinated water so obtained may be used for food, agricultural or industrial uses.

The reverse osmosis process is known and involves the passage of solvent molecules through a semipermeable membrane from the liquid to be treated to the permeate liquid, while applying a pressure higher than osmotic pressure to the liquid to be treated.

Such semipermeable membrane is a selectively permeable membrane, which is highly permeable to solvent molecules , and very poorly permeable to solute molecules, such that the solute is retained in the liquid part to be discarded, generally called concentrate or brine, and the low salt concentration permeate may be thus obtained.

The fluid to be treated shall be pressurized to a pressure higher than osmotic pressure for reverse osmosis to occur, whereby some mechanical work is required, which is generally performed by a hydraulic pump .

The concentrate liquid that flows out of the desalinator is still at high pressure, and hence has a pressure energy that can be advantageously recovered to increase the overall energy efficiency of the device.

Desalinators having energy recovery systems are known and widely used in large-scale seawater desalination plants, which typically process feed water amounts of the order of several hundreds of thousands of liters per hour.

In smaller scale devices, such as those designed for use in the naval industry, the combination of high pressure required for reverse osmosis and low flow rate makes the energy recovery systems of large- scale desalinators ineffective.

Typically, small-scale desalinators use energy recovery systems and directly discharge the pressurized concentrate liquid.

Therefore, prior art desalinators of this size require large pumps, which are required to handle the whole work of pressurizing the liquid to be treated, and have a low energy efficiency.

Therefore, the present invention has the object of obviating these drawbacks using a desalinator as described hereinabove, wherein the energy recovery device also consists of at least one hydraulic turbine at the outlet of said one or more filter units, which hydraulic turbine is mechanically connected to drive an auxiliary pump at the inlet of said one or more filter units and connected in series with said feed pump.

In a preferred embodiment, the hourly permeate liquid production of the desalinator of the present invention ranges from 200 to 2000 liters/hour.

The above relatively simple and inexpensive arrangements were surprisingly found to be able to provide an energy recovery device that affords up to 90% energy recovery in desalinators characterized by 200 to 2000 liters/hour hourly permeate production rate .

Thus, the pressure of the concentrate liquid that comes out of the filter unit is not dissipated, and is used to operate a hydraulic turbine which in turn drives an auxiliary pump at the inlet of the filter unit.

The auxiliary pump assists the action of supplying the liquid to be treated performed by the main feed pump, whereby the main feed pump may have a smaller size than in prior art desalinators.

Due to its osmotic membranes, the filter unit can process a 100% liquid to be treated to obtain about 20% zero-pressure permeate and 80% high- pressure concentrate liquid. In a further exemplary embodiment, means for controlling the hourly permeate liquid production rate are provided.

Such means for controlling the hourly permeate liquid production rate may advantageously comprise a flow control valve of any type, particularly a throttle valve.

Such hourly liquid production rate may be set from a minimum value of 200 to a maximum value of 2000 liters/hour.

The hourly permeate liquid production rate may be also programmed to change according to a predetermined time function.

In a further embodiment, a control panel is provided for turning on/off the desalinator and for setting said means for adjusting the hourly production of permeate liquid.

The control panel manages a quick and intuitive user interface for controlling and monitoring the desalinator .

In a further exemplary embodiment, the pressure of the liquid at the inlet of the filter unit ranges from 40 to 70 bar, preferably from 50 to 60 bar, and is particularly substantially 55 bar.

Such flow rate and pressure combination, as well as the efficiency afforded by the energy recovery device provides a device that has a compact size, also due to the small size of the feed pump, can be manufactured in a relatively simple manner, and has low energy consumption.

The use of a hydraulic turbine mechanically connected to drive an auxiliary pump further provides the important advantage of not requiring a predetermined operating position for operation of the desalinator, and actually allowing operation of the desalinator in any position.

All the above aspects male the desalinator of the present invention particularly suitable for the naval industry.

Advantageously, the feed pump or the auxiliary pump may be of any type, and according to an exemplary embodiment, the feed pump and/or the auxiliary pump are of positive displacement and/or fluid-dynamic, particularly centrifugal type.

In a variant embodiment, a plurality of filter units are provided, which filter units can be connected and disconnected with and from each other in series and/or in parallel .

This will impart modularity to the system, such that the operating osmotic membranes may be increased or decreased, and the production of permeate liquid may be managed in different manners according to the type of liquid to be treated.

In a further exemplary embodiment, a mechanical filter unit is provided for said liquid to be treated.

Such mechanical filtering unit allows removal of suspended impurities from the liquid to be treated before supplying it to the reverse osmosis filter unit .

In a further embodiment means are provided for monitoring quality parameters of the permeate liquid, which may advantageously be sensors located in the permeate liquid supply line.

In a further embodiment, means are provided for function diagnostics, which diagnostic means generate alarm signals in case of malfunctioning. Particularly, the diagnostic means are connected in a wired or wireless con iguration to a remote operations control center.

The present invention further relates to a kinetic and/or pressure energy recovery device, for recovering energy from a pressurized liquid flow 7 leaving a hydraulic system, which device comprises at least one hydraulic turbine at the outlet of said hydraulic system, which hydraulic turbine is mechanically connected to drive an auxiliary pump at the inlet of said hydraulic system, wherein said pressurized liquid flow ranges from 800 to 8000 liters/hour and the pressure of said pressurized liquid ranges from 40 to 70 bar, preferably from 50 to 60 bar, and is particularly about 55 bar.

These and other features and advantages of the invention will be more apparent from the following description of a few embodiments shown in the accompanying drawings, in which:

Fig. 1 is a schematic view of a prior art device ;

Fig. 2 is a schematic view of a device of the present invention;

Figs. 3 to 6 are several views of one embodiment of the device;

Figs. 7 and 8 are two views of the pump's runner ;

Figs. 9 and 10 are two views of the turbine's runner ;

Figs 11 to 13 are several views of the pump's body;

Figs 14 to 16 are several views of the turbine's body. Figure 1 shows a schematic view of a prior art device, having a supply line for a liquid to be treated 6, a feed pump 5 for supplying the liquid to be treaded 6 into a filter unit 2, which filter unit 2 comprises osmotic membranes for reverse osmosis filtration .

A permeate liquid 8 and a conduit for the concentrate liquid 7 extend from the filter unit 2.

For desalinators characterized by an hourly production of permeate ranging from 200 to 2000 liters/hour, with an operating pressure at the inlet of the filter unit 2 of about 55 bar, the concentrate liquid that leaves the filter unit 2, which is still under pressure, is released with no energy recovery.

In the device of the present invention, which is shown in schematic form in Figure 2, a kinetic and/or pressure energy recovery device 4 is introduced.

In a preferred embodiment, the hourly permeate liquid production rate of the desalinator of the present invention ranges from 200 to 2000 liters/hour and the pressure of the liquid to be treated at the inlet of the filter unit 2 ranges from 40 to 70 bar, preferably from 50 to 60 bar, and is particularly substantially 55 bar.

In the illustrated example, the energy recovery device 4 consists of a hydraulic turbine 9 at the outlet of the filter unit 2, which hydraulic turbine 9 is mechanically connected to drive an auxiliary pump 10 at the inlet of the filter unit 2 and connected in series the feed pump 5.

The connection between the hydraulic turbine 9 and the auxiliary pump 10 may be ensured by any kinematic chain. Advantageously, the hydraulic turbine 9 and the auxiliary pump 10 are mounted to a common shaft 11.

Either a single filter unit 2 or a plurality of filter units 2 may be provided, which filter units 2 can be connected and disconnected with and from each other in series and/or in parallel .

Figures 3, 4, 5 and 6 show several views of an exemplary embodiment of the device of the present invention .

The device comprises a feed pump 5 which is driven by a motor; advantageously, such motor is an electric three-phase motor.

The feed pump 5 and the auxiliary pump may be of any type, such as positive displacement or fluid- dynamic, particularly centrifugal pumps.

In the illustrated example, three filter units 2 are provided.

The desalinator 3 has a mechanical filter unit 3 for the liquid to be treated 6, which is adapted to remove suspended impurities from the liquid to be treated 6 before supplying it to the reverse osmosis filter unit 2.

The desalinator also has a frame 12, which is composed of tubes connected together by joints and can be adapted to the sizes of the number of filter units provided therein. Particularly, the frame is divided into several sections: at least one intermediate frame extending section and two lateral end sections .

The lateral end sections include the posts and the elements that define the corner areas of the frame, which consist, for instance of three sub- elements oriented in three different directions, which define a corner area of the frame 12. The posts may include intermediate elements, each having means for removable mechanical connection to an additional part, which may either consist of the corner area end part, or an additional intermediate element.

This particular construction of the frame 12 allows the overall size of the desalinator to be selected for installation in predetermined spaces and/or for connection of a predetermined number of filter units 2. Means for controlling the hourly permeate liquid production rate may be provided, which may advantageously comprise a flow control valve of any type, particularly a throttle valve.

A control panel is also provided for turning on/off the desalinator and for setting the means for adjusting the hourly production of permeate liquid.

Advantageously, as shown in the figures, the desalinator is very compact, since it is substantially comprised in a parallelepiped, the top surface being constituted by the control panel.

The filter units 2, preferably in the number of three, are placed side by side within the frame 12 in order to reduce the overall dimensions.

The frame 12 constitutes also the supporting structure for the control panel 1.

Means for monitoring quality parameters of the permeate liquid and/or means for function diagnostics may be also provided, which diagnostic means generate alarm signals in case of malfunctioning.

Particularly, the diagnostic means are connected in a wired or wireless configuration to a remote operations control center.

Figures 7 and 8 show two different views of the runner of the auxiliary pump 10.

The runner of the auxiliary pump 10 is formed by two discs, a first disc 16 connected to the hub and a second disc 17 providing a frontal closing cover, with a central feeding hole 18, and between the two discs are provided conveying surfaces that constitute the blades 15 of the runner.

The runner of the auxiliary pump 10 comprises five equidistant blades 15, which extend angularly for approximately 135°, as seen in Figure 7, starting from a central point of the runner, near the hub, and terminating on the peripheral edge of the runner.

The angular development of the blades 15 is as follows, where Pos is the angular position starting from point 13 to point 14, RE is the external radius and RI is the internal radius in mm.

The runner of the turbine 9 is built similarly, as shown in figures 9 and 10, comprising a first disc 22 and a second disc 23 provided with a central feeding hole 2 .

The runner of the turbine 9 comprises seven equidistant blades 21, which extend angularly for approximately 135°, as seen in Figure 9, starting from a central point of the runner, near the hub, and terminating on the peripheral edge of the disc.

The angular development of the blades 21 from point 19 to point 20 is as follows.

Preferred embodiments of the body of the turbine 9 and of the auxiliary pump 10 can be seen in figures 11 to 16.

This preferred embodiment provides, for a permeate rate of 200 1/h, an energy recovery of 1 KW and a cubature of 500x500x1000, equivalent to 60 Kg, at a speed of 10 m/sec, while for 2000 1/h it provides an energy recovery of lOK and a cubature of 1000x1000x1000, equivalent to 200 Kg, at a speed of 10 m/sec.

Claims

1. A reverse osmosis desalinator comprising an inlet conduit for a high salt concentration liquid to be treated (6) , a feed pump (5) for supplying said liquid to be treated (6) into one or more filter units (2) comprising at least one osmotic membranes, which one or more filter units (2) are connected to at least one outlet conduit for the permeated liquid

(8) , i.e. a liquid whose salt content is lower than that of the liquid to be treated, and to at least one outlet conduit for the concentrated liquid (7), i.e. the liquid part having a high salt content, with the salt fraction extracted from the permeated liquid dissolved therein, and which concentrated liquid is to be discarded, further comprising at least one energy recovery device (4) for recovering the kinetic and/or pressure energy of said concentrated liquid (7) at the outlet of said one or more filter units (2) ,

characterized in that

said energy recovery device (4) consists of at least one hydraulic turbine (9) at the outlet of said one or more filter units (2) , which hydraulic turbine

(9) is mechanically connected to drive an auxiliary pump (10) at the inlet of said one or more filter units (2) and connected in series with said feed pump (5) .

2. A reverse osmosis desalinator as claimed in claim 1, wherein the hourly production of desalinated liquid (8) ranges from 200 to 2000 liters/hour.

3. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein means are provided for adjusting the hourly production of permeated liquid (8) .

4. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein a control panel (1) is provided for turning on/off the desalinator and for setting said means for adjusting the hourly production of permeated liquid (8) .

5. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein the pressure of said liquid at the inlet of said one or more filter units (2) ranges from 40 to 70 bar, preferably from 50 to 60 bar, and is particularly substantially 55 bar.

6. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein said feed pump (5) and/or said auxiliary pump (10) is/are of positive displacement and/or fluid dynamic type, particularly of centrifugal type.

7. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein a plurality of filter units (2) are provided, which filter units (2) may be connected and disconnected with and from each other in series and/or in parallel .

8. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein a mechanical filter unit (3) is provided for said liquid to be treated (6) .

9. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein means are provided for monitoring quality parameters of said permeated liquid (8) .

10. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein means are provided for function diagnostics, which diagnostic means generate alarm signals in case of malfunctioning .

11. A reverse osmosis desalinator as claimed in one or more of the preceding claims , wherein said diagnostic means are connected in a wired or wireless configuration to a remote operations control center.

12. A kinetic and/or pressure energy recovery device, for recovering energy from a pressurized liquid flow (7) leaving a hydraulic system.

characterized in that

it comprises at least one hydraulic turbine (9) at the outlet of said hydraulic system, which hydraulic turbine (9) is mechanically connected to drive an auxiliary pump (10) at the inlet of said hydraulic system, wherein said pressurized liquid flow (7) ranges from 800 to 8000 liters/hour and the pressure of said pressurized liquid (7) ranges from 40 to 70 bar, preferably from 50 to 60 bar, and is particularly about 55 bar.